The present invention relates to on-board weather radar for use on aircraft or other vehicles. More particularly, the present invention relates to methods and apparatus for providing ground-based weather radar information to a pilot using existing on-board weather radar indicators.
Weather has been identified as a cause or contributing factor to nearly 25% of aviation accidents and 35% of fatalities. Accidents occur when a chain of events leads to a failure of an aircraft system, a mistake on part of the crew piloting the aircraft, or a combination thereof. Improved levels of weather information and the use of pilot decision aids may be helpful in breaking the chain of events that leads to an accident.
In addition to creating hazardous situations, weather is a common cause of flight delays. For example, in the United States, more than 70% of delays are attributed to weather conditions. While the industry will always have some level of delay caused by extreme weather, there is a growing belief that improved weather information in the cockpit could improve efficiency for the overall system.
On-board weather radar is a tactical navigation aid that shows convective hazards for the next 15 to 30 minutes of flight. The on-board weather radar currently serves as the focus of a pilot""s awareness of the weather situation. It provides a graphical depiction of precipitation relative to the aircraft""s position. The presence of turbulence can be inferred from these reflections off of precipitation. Through the use of Doppler processing, turbulence can also be detected and displayed directly.
While the on-board weather radar has proven invaluable as a real-time source of tactical weather information, the range is limited. Additionally, the beam width of on-board weather radar increases significantly at longer ranges, making it difficult to perform fine resolution of precipitation patterns.
To enhance safety and efficiency, government and industry are attempting to improve the availability and quality of weather information available to flight crews. It is desirable to provide flight crews with weather information which has been up-linked from a ground-based weather radar system. One such ground-based weather radar system is the Next Generation Weather Radar (NEXRAD) system, the data from which is available via the Internet or other sources. These ground-based weather radar systems offer a strategic view of weather over a larger region than possible with on-board weather radar. The NEXRAD system includes ground-based radar sites distributed across the continental United States. The NEXRAD system is used to create a series of weather products, including base reflectivity, composite reflectivity, hail indices, and storm tracking information, to name a few. Generally, NEXRAD provides an excellent strategic view of the weather situation, but would likely suffer in cockpit applications from latencies due to acquisition, processing and up link.
The pilot community has expressed interest in up-linking ground-based radar images, like those available from NEXRAD, to the cockpit as has been proposed. Several industry-led programs have focused on development of applications for displaying these images in the cockpit of an aircraft. Generally, these efforts have assumed the presence of a relatively large, high-resolution display. However, many aircraft currently in service in the industry are not equipped with these types of displays, and further may not have the panel real estate to retrofit such a display. Consequently, a method of providing both on-board weather radar information and ground-based weather radar information to flight crews in aircraft having limited panel real estate would be a significant improvement in the art.
Providing the ground-based weather radar information to the pilot of the aircraft presents additional difficulties in existing avionics systems. The standard weather radar bus and indicator (display), which are ubiquitous in commercial and high-end general aviation aircraft, are limited in display capability provided by these mature standards. Therefore, a method of providing ground-based weather radar information to the pilot using existing flight decks would be a significant improvement in the art.
A method of integrating ground-based radar information into an existing on-board aircraft radar system, where a radar indicator displays on-board radar images as a function of data words received from a receiver/transmitter of the on-board aircraft radar system, includes receiving ground-based radar data indicative of a ground-based radar image. A data word from an output stream of the receiver/transmitter of the on-board aircraft radar system is captured, with the captured data word being encoded in a first data word format. A position and heading of the aircraft is determined, and the ground-based radar data is sampled to obtain sampled ground-based radar data corresponding to the position and heading of the aircraft and to a radial scan angle for the captured data word. The sampled ground-based radar data and the captured data word are combined into a composite data word, with the composite data word being encoded in the first data word format. The composite data word is provided to the radar indicator for use in displaying a composite weather radar image having both on-board weather radar imagery and ground-based weather radar imagery.